Pneumatic hammer



lw 1934- A. A. HEITZMAN El AL 1,954,411

PNEUMATIC HAMMER Filed July 25, 1930 2 sheets sheet 2 ATTORNEY PatentedApr. 10, 1934 PATENT OFFICE 1,954,411 PNEUMATIC VHAMM'ER.

Alfred A. mam, West New York, and Charles R. Heitzman, Grantwood, N. J.

Application 25, 1930, Serial No. 470,583

2 Claims.

Our present invention relates to pneumatic hammers wherein thereciprocating driving member is driven by compressed air against a toolholder in which a tool is held; and it belongs.

5 to that type of pneumatichammer wherein a reciprocating pistonarranged within the hammer operates the reciprocating plunger. In thistype of hammer the piston is driven by eccentric means, such as a crank,operated either by a motor connected directly to the crank shaft or by amotor detached from the tool and connected for operation with the hammerby means of a flexible shaft. This type of hammer differs from thepneumatic hammers operated. by compressed air fed through a hose from acompression tank, in that the compressed air is generated within thehammer structure instead of being fed from an outside source to it.

There have been several attempts to provide pneumaticv hammers of thetype to which the present one belongs but, as far as we are aware,

in all previous hammers of this type the reciproeating plunger has beendriven downwardly for the impact blow through air compressed between thepiston and the plunger by the movement of the piston, and it has beenreturned by suction action caused by the backward suction of th pistonon its return stroke.

The object of the presentinvention is to provide a hammer having apiston operated by mechanical means such as a crank, the pistonreciprocating within the sleeve which fits within the cylinder: of .thehammer structure;- and the reciprocating plunger which is operated bythe hammer, is not only driven downwardly through the air which iscompressed between the piston and plunger, but after the completion ofthe downward stroke the plunger is returned bycompressed air admittedtemporarily below the plunger to force it upwardly in making its returnstroke simultaneously with the, return stroke of the piston. One objectof'this combination is that it is not necessary to completely changefrom a condition wherein compressed air occupies the space between thepiston andthe plunger at one time and where a high vacuum is necessarybetween the piston and the plunger at another time. The basicdifierence, therefore, between the present hammer and those of the priorart resides in'the features which cause-the driver or p'unger to bereturned by compressed air generated by the reciprocating piston andwhich is valved or controlled by the plunger itself, so that thecompressed air which returns the plunger is thispiston and which is thedriving member pfadmitted into the sleeve below the plunger at thecompletion of the downward blow.

Some of the advantages of this combination are that the hammer may beoperated at the same speed as the motor which operates the shaft of thehammer and the plunger will make the same number of strokes as the shaftthrough which it is operated.

Another and very important feature of the invention is that there isvery slight reaction on the handle of the hammer, so that the operatoris not subjected to the hard, rapid vibrations heretofore caused by allprevious types of hammers. As a result the operator is not injuriouslyafiected even though the present hammer is operated continuously forlong periods. Whereas heavy hammers heretofore used have disabled theoperators and limited the periods of use of the hammer to afew hours ata stretch, with the present type of hammer an operator may workcontinuously for a full day-and from day to day without injurious efiectbecause of the fact that the'reaction upon the handle by which thehammer is manipulated is almost negligible and it does not injure theoperator as have the previous devices.

Another advantage eflected by reducing the vi-' bration on the handle isthat the .operator may more accurately guide and control the hammer inorder to control the operations of the tool,

thereby executing whatever work isbeing done with greater accuracy'thanis possible with hammers in which the vibrations seriously react uponthe operators hands and arms. The reaction upon the driving shaft andmotor is likewisereduced or cushioned, thereby reducing wear and tearupon the motor and rendering its operation more smooth. v v

' Anotheradvantage of the presenthammer yis that fora givensize'and witha giventype of motor more powerful blows are delivered by the plungerand this is accomplished also with a practically negligible reactionuponthe handle and therefore upon the operator. 'Thereis also greaterefliciency in the energy delivered by the plunger from a given size andtype of hammer operated by a motor of given power so that the presenthammer is more eflicient from the stand point of energy output comparedwith 1' energy input. Another advantage or the present invention is thatthe plunger is provided with a cup'or recess adapted'to receive thereinan extension'on the piston so that the return action onthe' plunger is.cu hioned in relationto the piston; but in the 110 tit present casethese parts do not have to be made with as fine clearance as in previoushammers.

Another advantage is that these co-operating parts do not have totelescope to the same extent as in former hammers where a high vacuum iscreated between the plunger and piston. In addition, the plunger willnot hold to the piston and fail to be driven the full extent necessaryto deliver the blow. Other advantages will be apparent from thefollowing description of one form of our invention.

While many of the parts of the present device resemble in appearance theprincipal parts of devices in the art, nevertheless there are cer taindiiferences so that they co-ordinate in producing satisfactory results.

In the drawings forming part of this application,

Figure 1 is a vertical sectional view through a hammer embodying ourinvention, and is taken on the line 11 of Figure 4,

Figure 2 is a cross sectional view, taken on the line 2-2 of Figure 1,

Figure 3 is a similar view taken on the line 3-3 of Figure 1,

Figure 4 is a longitudinal, sectional view and is taken on the line 4-4of Figure 1,

Figure 5 is a perspective assembly view of various parts of the hammer,

Figures 6, 7 and 8 are longitudinal sectional views showing thepositions of different parts of the hammer during different periods of acomplete stroke of the plunger, and

Figure 9 is an elevation of a hammer having the operating motor mounteddirectly thereon.

We will first describe the preferred construction of our hammer. We willthen describe what we now believe to be the-sequence of the actionstaking place within the hammer, butas we are dealing with parts whichare actuated through a fluid (air) which cannot be seen, this is givenmerely as our present belief of the operation and subsequent events maypartly contradict the same. However, the construction of the hammer andthe results obtained with it have been clearly demonstrated by actualtests.

In the drawings we have shown the working parts of the hammer arrangedin a casing 1 which has a gradually tapered shank 2 which carries thetool holder at its lower end. The upper portion of the casing is shownas en arged at 3, and the handle or grip 4 is shown as cast integraltherewith to provide a member to be gripped by one hand of the operatorat the top of the hammer and the other hand may grip some portion-of theshank 2 to partly hold and to guide the device.

It will be understood that the shape of the casing here described is notimportant to the operation of our invention and it may be modified asdesired. The shank portion 2 of the casing is'provided with a centralbore 5 extending from the lower end thereof up to the enlarged portion 3of the casing. The lower end of this bore is provided with an internalthread 6 to permit the externally threaded sleeve 7 to be screwed infrom the lower, open end of the casing,

Above the threaded portion 6 the bore 5 is cylindrical, and smooth up tothe point where a shoulder 8 is formed to provide a seat or abutment forone end of the sleeve 9 which serves as a liner and as a raceway for thepiston and plunger. The upper portion of the casing is provided with alaterally extending bore 40 shown as running at right angles to the bore5 and incommunication with the upper end of the latter. This bore willbe referred to hereinafter.

There is a preferably round, cylindrical sleeve 9 which fits snuglywithin the vertical bore 5, lying above the threaded portion 6 thereofand as this sleeve must be sta-tionarily held within the casing whilethe hammer is in operative condition, we have shown it fitting snugly,in the smooth portion of the bore 5 with one end (the upper) of thesleeve abutting against the shoulder 8 near I the top of the bore 5.There is a washer 10 which is pressed against the lower end of thesleeve 9 by the outer sleeve 7 which is screwed into the threadedportion 6 of the bore 5. The sleeve '7, therefore, serves to hold thesleeve 9 pressed against the shoulder 8, to retain it in fixed positionwithin the casing, but permitting it to be disassembled when necessary.The end sleeve 7 is itself locked in position in the lower end of thecasing by a locknut 11.-

The sleeve 7 has a bore 12 in which the tool holder 13 is adapted toreciprocate and to be guided; and the tool holder is also adapted toproject through an aperture 14 in the washer 10 so that this washer alsoassists in guiding the tool holder during its reciprocating motion. Noparticular tool is shown in the tool holder as it is to be understoodthat the tool holder follows previous practice and the manner ofattaching the tool therein, as well as the variety of tools which may beinserted in the holder are all well known in the art.

The sleeve 7 is provided above the bore 12 with a larger bore 15 whichforms a chamber for housing a coiled spring 16 which surrounds the shank1 17 of the tool holder and which spring is compressed between thestationary washer 10 at the upper end of the sleeve 7 and the washer 18which is movable with the shoulder 19 on the shank of the tool holder,and which is limited in its movement in one direction by the shoulder19' of the sleeve 7. The spring 16, therefore, resists upward movementof the tool holder in the bore 12 and the guiding aperture in thestationary washer 10 and it tends to move the tool holder to theposition shown in Figure 1. Upward movement of the tool holder willcause the shoulder 19 to carry the washer 18 with it and compress thespring 16 and when upward pressure on the tool holder decreases, thespring 16 returns the tool holder to the position shown in Figure 1.

'The sleeve 9, as above described, fits the bore 5 snugly, but we haveshown this sleeve provided with longitudinal grooves 20, on oppositesides, as one means of forming spaces or passages between the sleeve andcasing for the fluid (air) to travel back and forth lengthwise of thecasing. This sleeve is notched as shown at 21 at the upper terminal ofthe grooves 20 so that these grooves are in fluid communication with thebore 5 above the piston.

The sleeve 9 is also provided with one or more ports 22 (two being shownarranged opposite each other), the positions of which in relation to themovements of the plunger will be referred to more particularlyhereinafter. These ports form a means of communication for the fluid(air) to pass from the bore 23 of the sleeve into the grooves 20 andvice versa, from the grooves back into the bore of the sleeve.

At or near the lower end of the sleeve 9 there is a port 24, two beingshown disposed opposite each other, which form another means ofcommunication for the fluid or air to pass from the bore 23 of thesleeve into the grooves 20 and vice motor;

aligned sections 29, 30 which are journaled by Preferably, the ports 24are formed close to the bottom end of the sleeve 9 as shown in thedrawings, for a purpose which will be made more apparent in thedescription 'of'the operation of the invention.

There is a plunger 25 which forms the percussion member of the hammerand therefore it is of sufficient weight to deliver a .percussive blowto the upper end of the tool holder which pro-! jects above the fixedwasher 10. This plunger has a free. sliding fit in the bore 23 ofthesleeve .9 but the clearance is nevertheless such as will prevent anysubstantial movement of the fluid (air) between the plunger and theinner surface of the bore'23. i I

Above the plunger we have arranged a reciprocating piston 26 which alsohas a free, slding engagement with the bore .of the sleeve 9 but ,theclearance here, also, is such as to prevent substantial passage of airbetween the periphery of the piston and the surface of the bore 23. Theupper end of the plunger 25 is preferably providedwith a recess 27 andthe lower end of the piston is provided with a corresponding projection28 adapted to telescope withn the recess 2'? but, whereas'these membershave heretofore had to be very carefully and accurately machined andlapped to provide a very close fit, in the present case such refinementin finishing these parts is not necessary.

Furthermore, in former devices the clearance between the projection 28and the wall of the recess 27 has been so small that the plunger did notalways leave the piston but clung to it,- travelling back and forth andfailing to deliver a blow upon the tool holder.

Any means may be employed for reciprocating the piston and we have shownby way of example a crank which revolves with a shaft mounted in theupper portion of the casing and driven by a There is a cross shaftcomposed of two means of ball bearings 31 in socket 32 in theeasingabove the bore 5 and crosswise in relation to the axis of thelatter. One section 29 of this shaft has an integral arm 33 whichcarries a pin 34 projecting laterally therefrom to form part of a wristpin; and the .axis of this pin is, offset or spaced from the axis of theshaft section 29 corresponding with the thrust of the crank andtherefore the stroketo be made by the piston 26.

The other member 30 of the shaft has an arm 35 and this has a hollowmember 36 projecting laterally therefrom and adaptedto telescope overthe pin 34 whereby these two members form a wrist pin the parts of whichtelescope and permit the shaft sections to be placed into and removedfrom the compartment of the casing separately.

Preferably, the two crank arms 33, 35 are counterbalanced for smoothoperation and for this purpose there are arms 37, 38 extending inopposite directions from the crank arms 33, 35 and each is provided witha counterweight 39 for the purpose of counterbalancing the weight ofthearms 33, 35 and the members of the wrist pin.

One end of the bore 40 in which the crank is housed is closed by a cap41 which has a threaded portion 42 which screws into the threaded end ofthe bore 40 which is the left hand end in Figure 4. There is a sleeve 43journaled in the cap 41- and connected to revolve with the shaft section30' and the end of a flexible shaft (not shown) which is operated from adriving motor (not receive oil for oiling all the movable parts of thehammer. There is avalve cap45 screwed into the outer end of this oilport and it contains a check valve shown herein as a ball 46 seatingagainst a valve seat in the'cap 45. This serves as a check valve toprevent compressed air from escaping through the oil port from theinterior of the easing and it permits air to be drawn into the casing bythe piston, for compression therein.

The wrist pin of the crank is connected with the piston by a connectingrod 47 having a hub 48 which fits around the wrist pin; and the otherend of the connecting rod has a ball 49 which fits into a sphericalsocket 50 in the upper end of the piston, where it is held fromwithdrawing by the swaged flange 51.

Operation-At each revolution of the shaft the crank acts through theconnecting rod 47 to reciprocate the piston 26, the latter making onecomplete stroke down and up for each revolution of the shaft and crank.

If the motor which operates the shaft and crank is set into operationthe piston will be reciprocated but the plunger will not be operatedunless the tool is pressed against the piece of work. Unless the tool ispressed against a piece of work the upper end ofthe shank 17. of thetool holder will not extend into the path of the plunger, as shown inFigure 6 and therefore the plunger will rest upon the washer 10 and itslower end will close the ports 24 in the sleeve 9. At such times thepiston may reciprocate under the. action of the crank but theplunger-will simply rest idly on the washer 10. If the piston isreciprocating it will compress the air in the sleeve 9. This air is incommunication with the air in the grooves 20 through the ports 22 andthe air in the grooves is also in communication with the air in thecrank chamber. As the piston reciprocates it causes the check valve 46to alternately open and close and n the pistonwill build up acompression in the air within the casing. This is made apparent if thecheck valve is pressed inwardly by the hand to unseat it, in which casecompressed air will escape past the check valve and 'will make a soundas it escapes. While the part of the shaft which extends through thecasing has not an air-tight fit in the casing, nevertheless it is closeenough so that the rapidly acting piston can build up compression in theair within the casing after a. few strokes and maintain an appreciablecompression.

As stated above, the plunger will remain down and idle and the pistonwill simply build up a limited compression in parts of the casing aslong as the tool is not pressed upon the work.

But as soon as the tool is pressed on the work the tool holder movesupwardly in the bore 12 and in the aperture 14 of the washer 10, and theer 25 and lifts the plunger, the extent depending upon the downwardpressure of the tool upon the work, and which pressure overcomesther'esistance of the spring 16. The plunger is shown in idle positionin Figure 6. When the tool holder presses the plunger upwardly, however,as shown in Figure 7, the upward displacement of the plunger will causeits lower end to uncover the ports 24. At once the compressed air fromthe grooves 20 rushes in through the ports 24 and into the bore 23 ofthe sleeve 9 and between the washer 10 and the lower end of the plunger.This compressed air acts upwardly against the bottom of the plunger asindicated by the arrows in Figure 7 and lifts the plunger. When theplunger first moves upwardly in the manner above described, it closesthe ports 22 and they remain closed until the plunger goes down.

As stated above, the compressed air admitted below the plunger tends toand does move the plunger upwardly in the bore 23 of the sleeve 9,following the upward movement of the piston. The air above the piston isat this time so displaced that it tends to drive the air which is in thegrooves 20 through the ports 2% and thus lift the plunger.

In Figure 7 the piston is shown at the end of its upwardstroke and theplunger is shown at what we believe to be its uppermost position.

As the crank. reverses the movement of the piston the latter is drivendownwardly and it will drive the plunger down at the same time. Duringthis downward movement of the piston it acts through the air which liesbetween the piston and plunger and in the bore 23 to force the plungerdownwardly. While the plunger is moving downwardly the air in the bore23 which is below the plunger is being driven out through the ports 24into the grooves 20. This action of the air is aided by the fact thatthe air is being drawn into the bore 23 above the piston by thedownwardly moving piston, so that the air is rapidly displaced frombelow the plunger.

When the plunger is near the end of its downward movement it will strikethe shank 17 a percussion blow and the blow is transmitted through thetool holder to the tool and is thus applied to the piece of work,whatever it may be. The blow of the plunger drives the tool holder downmore or less and the spring 15 is partially compressed. The lower end ofthe plunger partly or wholly closes the ports 24, depending upon how fardown the plunger goes. The recoil of the tool and the tool holder againlifts the plunger and the cycle of operations above described isrepeated.

The force of the blow may be regulated by varying the pressure of thetool on the piece of work.

The greater this pressure, the more the shank will press the plungerupwardly on the recoil and so the ports 24 will be initially opened agreater extent and the quicker will the air rush through them and pressupwardly on the plunger to raise it to a greater extent for thesucceeding downward blow. Therefore, the force of the blows of theplunger is increased as the tool is pressed harder onto the work.

When the plunger reaches the end of its downward stroke it uncovers theports 22 and the air which is in the bore 23 and between the piston andplunger is equalized with the air in the grooves 20 until the recoiltakes place and the plunger closes the ports 22.

When the plunger and the piston are about to reach their extreme, lowerposition the projection 28 moves into the recess 27 in the plunger andthe air within the latter is highly compressed so that the plunger isalmost positively driven by the piston near the bottom of its stroke.When the piston is at the bottom of its stroke the ports 22 areuncovered so that air mayrush into the space within the bore 23 andbetween the piston and plunger to reduce the tendency of the piston andplunger to be held together by suction. As the piston begins to make itsupward move- 1,954,4.11 v ment, the projection 28 moves out of therecess 27 and remains so during most of the upward stroke. If the upwardstroke of the plunger is rapid and creates considerable momentum in theplunger, the plunger will not strike a metal-tometal blow on the pistonand therefore will not react strongly upon the operator through thehandle of the hammer.

If by chance the plunger should move with great speed and energy duringits upward stroke, the parts 28 and 27 will telescope more or less andcushion the action between the plunger and the piston, but at no timewill the extreme upper edge of the plunger strike the shoulder at theupper end of the projection 28 of the piston.

It will be observed from the above description taken in connection withthe accompanying drawings that the plunger is driven both downwardly andupwardly through the action of air under compression so that in no partof the hammer is it necessary to alternate between a condition ofcompression and rarefication in the air. This broadly distinguishes fromthe prior art because in the latter the plunger is always reiurned bysuction action as distinguished from the action of the compressed air.

In Figure 9 we have shown the hammer constructed with the motor mountedin an extension of the hammer casing. In this view the shank 60 of thecasing corresponds with the shank 2 in the first described form and theenlarged portion 61 corresponds with the enlarged portion 3 of thecasing. All of the parts'within the casing are exactly like those firstdescribed. Instead, however, of the motor being separate from the hammerand attached to the shaft by the flexible shaft the electric motor isdisposed within the housing 62 which is bolted to a flange 63 formed onone side of the casing. In this case the shaft of the motor is eitherintegral or connected with the shaft member 30 previously described. Forsome kinds of work it may be desirable to mount the motor on the hammerin the manner shown in Figure 9 but in this case the mechanism of thehammer is not changed. Having described our invention, what we claim 1s:

1. In a pneumatic hammer the combination of a casing constructed andarranged to permit an air pressure to be built up therein, a valve forpermitting inhaling and preventing exhaling of air in said casing, saidcasing having a raceway, a tool holder, a piston reciprocating in saidraceway, a plunger reciprocating in the same raceway between said toolholder and said piston, a member of said casing having a port forpermitting fluid to enter and leave said raceway in front of the end ofsaid plunger which faces said tool holder, said plunger being adapted toclose said port when it is adjacent said tool holder and to open saidport when it moves away from said tool holder, a member of said casinghaving a passageway forming a fluid-communicating means between saidport and the'side of said piston opposite that side which opposes saidplunger, whereby fluid under pressure may circulate between the space inthe raceway ahead of said plunger and the space at the rear of saidpiston, and means for reciprocating said piston.

2. In a pneumatic hammer the combination of a hollow casing having a,raceway, a tool holder,v

space above said piston, said channel adapted to permit air to passbetween the spaces at opposite ends of both said piston and plunger,said casing having a port to permit air below said plunger to enter andleave said channel adjacent the lower end of said plunger, said casinghaving a port to permit air in said raceway between said piston andplunger to enter and leave said raceway, said latter port being sodisposed as to be closed by said plunger during its upward stroke

